The approaches described in this section could be pursued, but are not necessarily approaches that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, the approaches described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
The Stream Control Transmission Protocol (SCTP) is a general-purpose transport layer protocol providing a service similar to TCP (Transmission Control Protocol) plus a set of advanced features to use the enhanced capabilities of modern IP (Internet Protocol) networks and to support increased application requirements. Nowadays, there are SCTP implementations for all major operating systems.
The SCTP protocol, as specified by the IETF, is used in 3GPP (3rd Generation Partnership Project) for transporting signaling information within a cellular core network. SCTP was designed to address certain limitations inherent to TCP for the transport of signaling for telephony over IP. One of the main design goals of SCTP was the efficient transport of small messages in a network fault-tolerant way, important for transporting signaling messages. Thus, SCTP provides a reliable data transmission service for the transport of service messages to applications users.
SCTP is a connection-oriented general-purpose transport protocol that preserves message boundaries. An SCTP connection, called an SCTP association, can be used on top of IPv4 and IPv6.
The messages are encapsulated in data structures called chunks. The chunks are themselves encapsulated in SCTP packets. Moreover, SCTP incorporates several new features that are not available in TCP.
One of the most important enhancements provided by SCTP over traditional transport layer protocols is multihoming. This multihoming feature allows an SCTP association to use several source and destination addresses. Then, each node can be accessed by several addresses set at the establishment of the association. The addresses of transport are exchanged during the initialization of an SCTP association.
The multihoming feature was used up to now as a way to provide reliability. Whenever a primary path between a source and a destination fails, the SCTP association remains as a traffic can continue to flow over one of the secondary paths.
An SCTP association requires to have a bidirectional link for exchanges between two end-points. That's why, up-to-now, the various paths used in a SCTP session were generally bidirectional links.
In another context, unidirectional links are used, for instance broadcast networks, to deliver not only a broadcast or a multicast content but also a specific content destined to only one client, as a VoD (Video on Demand) content for instance. This is made possible thanks to such unidirectional networks topology which is similar to a tree as depicted in FIG. 1.
The topology represented in FIG. 1 contains one node 2 connected to a headend router 4 via a multiplexer 6. Three southbound trunks 8 are provided with a given number of clients 10 attached to each southbound trunk 8.
Thus, within this topology, there is not a unique and identical multiplex delivered to all the clients, this multiplex containing all the available broadcast content. Here, on each southbound trunk 8, a multiplex 12 is provided, that contains only the content requested by the clients 10 of the same trunk, and is not burdened with traffic that is useless for its clients 10. That's why, with this topology, some bandwidth is freed and can be used for other purposes, as delivering an individual, i.e. unicast, content.
Moreover, a broadcast network is managed so that a constant quantity of bandwidth can be allocated to a given content, which guarantees a given quality of service.
It is also known that cable TV operators' networks are called hybrid fiber-coaxial (HFC) since they combine optical fiber and coaxial cable, i.e. a unidirectional link and a bidirectional one. For a cable operator, it costs much more to deliver data over the broadband network than over the broadcast network. That's why the cable operators attempt to privilege this last broadcast link.
A broadcast network is a unidirectional network. It can be completed with a broadband network to provide a return channel but the synergy between both networks does not allow to leverage all existing delivery technologies to deliver content, especially an IP-based huge content, in an efficient way. For instance, existing broadcast networks and transport protocols do not allow to deliver a video content to a client using HTTP, or any other protocols on top of TCP. This means that an operator cannot complement its broadband network with the broadcast one to deliver video content using an HTTP streaming.
A protocol called UDLR (UniDirectional Link Routing) aims at emulating bidirectional capability for a unidirectional link by associating it with a bidirectional link and tunneling the uplink data through the bidirectional link. This solution however lacks bandwidth aggregation capability.
The paper “Using SCTP to improve performances of hybrid broadcast/telecommunication network system”, IEEE Consumer Communications and Networking Conference, 11-13 Jan. 2007, presents a network architecture based on the coupling of a GPRS (Generalized Packet Radio Services) up-link with a DVB-T (Digital Video Broadcasting-Terrestrial) downlink using the SCTP protocol.
Thus, this prior art paper uses a unidirectional network for the down-link and a bidirectional network for the uplink. Such architecture assumes that there is always an available bandwidth on the unidirectional, i.e. broadcast, network. However, such availability of the bandwidth cannot be guaranteed in practice.